Rust

Add binding for str.substr (#321) #551

Job	Run time
build_on_wasm	35m 45s
build_with_vcpkg_installed_z3 (linux)	1m 17s
check-formatting	11s
build_with_vcpkg_installed_z3 (macos)	1m 5s
build_with_bundled_z3 (linux)	16m 46s
build (macos-latest)	32s
build_with_vcpkg_installed_z3 (windows)	4m 43s
build (ubuntu-latest)	40s
run_clippy	27s
build_with_bundled_z3 (macos)	13m 18s
build_with_bundled_z3 (windows)	18m 51s
	1h 33m 35s

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